Control apparatus and control devices for use therein



Oct. 11, 1960 A. J. HILGERT 2,

CONTROL APPARATUS AND CONTROL DEVICES FOR use THEREIN Filed Aug. 6, 1956Heaf 23 Exch dryer IN V EN TOR.

Patented Oct. 11, 1960 CONTROL APPARATUS AND CONTROL DEVICES FOR USETHEREIN Adolph J. Hilgert, Milwaukee, Wis., assignor to Base Inc., acorporation of Wisconsin- Filed Aug. 6, 1956, Ser. No. 602,390

2 Claims. (Cl. 200-83) The present invention relates to controlapparatus and control devices for use therein, but more particularly toapparatus wherein a condition sensitive control device responds to agiven condition but only when said condition is provided in apredetermined manner or by predetermined means.

'Certain fluid fuel burning apparatus, particularly those wherein theheating unit is placed considerable distance from the chimney or stack,utilize fans or blowers of one type or another for moving exhaust gasesand other products of combustion from the bonnet or plenum chamber andtransmitting the same to the chimney or stack for flow to theatmosphere. Such fan or blower is particularly necessary in fluid fuelburning apparatus wherein the heating unit is relatively large withrespect to the air ducts which bring in secondary air for satisfactoryburning of the fuel emitted by the main burner and which afford removalof the products of combustion to the atmosphere. Without such fan orblower, the air within the combustion chamber might not be changedfrequently enough to afford adequate combustion of the main burner fuel(depending on the size of the heating unit with respect to the size ofthe air ducts), thereby causing exhaust gases and other products ofcombustion to accumulate within the combustion chamber and extinguishthe main burner flame and/ or prevent satisfactory ignition thereof.Such extinguishment of the flame at the main burner might not beaccomplished by extinguishment of the pilot burner flame, whereforeunburned fuel is emitted from the main burner into the enclosure of theheating unit. As is readily understandable, such a condition isextremely dangerous. In order to prevent occurrence of such a hazardouscondition, fan or blower means is provided to afford a constant supplyof secondary air to the main burner. However, since such fan or blowermeans is subject to malfunction and faulty operation, control meanscapable of distinguishing between satisfactory and faulty operation ofthe fan must be employed. In this regard, pressure sensitive controldevices have been utilized to sense the pressure variation within thebonnet as caused by satisfactory operation of the fan means.

Such pressure sensitive devices heretofore in use have usually employedelectrical contacts in the energizing circuit of a solenoid valve,which, as is understood in the art, requires 24 or 110 volts forsatisfactory operation. Because of the use of such relatively largeelectrical power, the electrical contacts of pressure sensitive devicesheretofore used could be exposed to the surrounding atmosphere or to theexhaust gases and other products of combustion without interferingappreciably with the life of the control device. However, the use ofoutside power, whether on the order of 24 or 110 volts, is undesirablesince it precludes the advantages inherent in self-powered units whichoperate on a minimal amount of electrical power (on the order of 25mv.). Electrical contacts for use in a low power circuit must be ofexceptionally low resistance, and hence cannot be exposed to foreignmatter which may have a deleterious effect on the life and operation ofsuch contacts. Thus such electrical contacts must be protected byenclosure means which does not disturb the sensitivity of the pressureresponsive device to changes in pressure caused by satisfactoryoperation of the exhaust fan.

It is therefore an object of the present invention to provide a pressuresensitive control device for use in low power circuits and which iscapable of distinguishing between pressure variations provided by meansemployed for that purpose and pressure variations caused by changes inatmospheric pressure.

Another object is to provide for use in low power circuits a pressuresensitive control device having cooperat ing control members enclosedwithin an hermetically sealed enclosure to prevent accumulation thereonof foreign matter, said control members being relatively movable betweencontrolling positions upon a predetermined variation in pressure butonly when such variation is caused in a predetermined manner.

Another object is to provide, for use in a thermo electric circuit, apressure sensitive control device which is extremely sensitive'topressure variations produced by means provided for that purpose.

Another object of this invention is to provide a pressure sensitivecircuit controlling device having hermetically sealed low resistanceelectrical contacts for use in a thermo-electric circuit, there beingmeans permitting response of said device to pressure variations causedin a predetermined manner only.

Another object is to provide heating apparatus having a pressuresensitive circuit controlling device, as characterized above, in circuitwith a thermoelectric generator and fuel flow control means for saidheating apparatus, said circuit controlling device being responsive topressure variations within the bonnet of the heating unit when caused bysatisfactory operation of a fan or blower in moving the products ofcombustion from within the bonnet to thereby permit energization of thefuel flow control means for supplying fuel to the main burner of theheating apparatus.

Another object is to provide heating apparatus in accordance with thepreceding paragraph and wherein said pressure sensitive device compriseshermetically sealed low resistance contacts for control of thethermoelectric current afforded by said thermoelectric generator.

Another object is to provide a pressure sensitive control device of thediaphragm type including a stationary contact, a movable contact fixedto the diaphragm, and hermetic enclosing means for protection of saidcontacts, said enclosing means comprising a stationary portion and aportion fixed relative to one side of said diaphragm, there being meansfixed relative to the other side of said diaphragm to compensate for theloss in effective area of the side of the diaphragm to which saidenclosure is fixed, whereby the area of the opposite sides of saiddiaphragm are maintained substantially equal so as to effectcancellation of atmospheric pressure variations exposed to both sides.

The novel features which I consider characteristic of my invention areset forth with particularity in the appended claims. The device itself,however, both as to its organization and mode of operation, togetherwith additional objects and advantages thereof, will best be understoodfrom the following description of specific embodiments when read inconnection with the accompanying drawing, in which the subject pressuresensitive control device is shown in section and connected, more or lessschematically, in circuit with fuel flow control means for a forced airheating unit.

Referring to the drawing, it shows a heating unit 10 comprising a sheetmetal shell or enclosure 12 providing a combustion chamber 14 and abonnet or plenum chamber 16. An air inlet duct 18 is affordedcommunication with combustion chamber 14 and an air outlet duct 20 isafforded communication with plenum chamber 16. A fan or blower 22 (notshown in detail) is operatively connected to outlet duct 20 for drawingproducts of combustion out of chambers 14 and 16 for expulsion to theatmosphere through a chimney or stack (not shown) as will hereinafterbecome apparent.

Positioned within enclosure 12 is a heat exchanger 23, there being anair inlet duct 25 and an air outlet duct 27 in communication therewithand extending through respective openings in enclosure 12. Air ducts 25and 27 are part of heat transmitting means for transmitting heated airfrom exchanger 23 through duct 27 to a space to be heated, and forbringing air to be heated into exchanger 23 through duct 25.

Positioned within an opening in the side wall of chamber 14, is a fluidconduit 24 having one end connected to a source of fluid fuel (notshown) and another end connected to a fluid flow control device 26. Oneend of a fluid conduit 28 is connected to control device 26 while theother end thereof is connected to a main fuel burner 30. Flow controldevice 26 comprises a flow control member or valve 32 havingflow-permitting and flow-preventing cooperation with a valve seat 34.Control device 26 is also provided with an electromagnetic operator 36having an electromagnet winding 37 energizable to effect movement ofvalve member 32 from its flow-preventing to its flow-permitting positionby means of an operating lever 38 pivotally mounted at 40. A returnspring 42 is provided for return of valve member 32 to itsflow-preventing position in engagement with valve seat 34 upondeenergization of electromagnet winding 37. A pilot or ignition burner44 is positioned adjacent main burner 30 for ignition thereof as is wellknown in the art, a pilot fuel supply conduit 46 affording communicationbetween pilot burner 44 and conduit 24.

Fixed to bonnet 16 within an opening formed therein, is a fluid conduit48 for transmission of fluid pressure from bonnet 16 to a conditionsensitive control device 50. Control device 50 comprises an enclosure 52formed of oppositely disposed cup-shaped members 54 and 56 havingsubstantially identical interior dimensions. Conduit 48 is affordedcommunicaiton with the interior of cup-shaped member 54 through anopening 54a formed in the latter, there being a compression fittingcomprising an externally threaded member 58 welded to or formedintegrally with cup-shaped member 54, a nut 60 formed with internalthreads for cooperation .with member 58 and a gas tight sealing member62 for gripping an enlarged end portion 48a of conduit 48 when nut 60 isfirmly threaded onto member 58.

interposed between cup-shaped members 54 and 56 is a pressure sensitiveactuating means in the form of a flexible diaphragm 64. Each of themembers 54 and '56 is formed with an annular flange 54b and 56brespectively, there being aligned openings for receipt of rivets 66 forfastening said members 54 and 56 in their oppositely disposed positionswith diaphragm 64 therebetween to provide separate pressure cavities orchambers 54c and 56c respectively. Positioned adjacent diaphragm 64within cavity 540, is a diaphragm reenforcing member 68. Attached tomember 68 as by welding or the like, is a movable mounting member 70carrying a movable control member in the form of an electrical contact72 formed integrally therewith or attached thereto in any well knownmanner. A stationary mounting member 74 is secured to cup-shaped member54 within cavity 540 and is formed With an opening 74a aligned with anopening 540! formed in member 54. I prefer to employ insulating glassseal mounting means 76 for retaining an elongated stationary controlmember in the form of an electrical contact member 78 in fixed positionrelative to mounting member 74. Mounting means 76 comprises a tubularbrass member 80 positioned within opening 74a and formed with an annularshoulder 80a in engagement with mounting member 74 as shown in thedrawing. interposed between member 80 and stationary contact member 78is an insulating member 82 formed of glass or ceramic material.

Member 54 is formed with a female connector portion 84 about opening 54dfor receipt of a male connector as is well known in the art. Positionedwithin opening 54d of member 54 and about the intermediate portion ofcontact member 78 is an insulating member 86, said contact member 78being formed with enlarged end portion 78a in engagement with member 86.Stationary contact member 78 is formed with a hemispherical electricalcontact 88 for cooperation with movable contact 72 as will hereinafterappear.

An electrically conductive expansible and contractible bellows 90 havingone end fixed to movable mounting member 70 and the other end fixed tostationary mounting member 74 afiords an hermetic enclosure for contacts72 and 88. I prefer to utilize a subatmospheric fill of inert gas forenclosure or bellows 90 to minimize chemical decomposition of contacts72 and 88 and to insure separation of said contacts in the event ofrupture of bellows 90.

Fixed to diaphragm 64 within cavity 56c is an hermetic enclosure 92formed substantially identically with the enclosure for contacts 72 and83. Enclosure 92 comprises a movable mounting member 94 formedsubstantially identically with mounting member 70 and an adjustablestationary end wall 96. An expansible and contractible enclosure orbellows 98 formed substantially identically with bellows 90 has one endfixed relative to movable mounting member 94 and one end fixed relativeto stationary end wall 96. Formed integrally with stationary end wall 96is a stud 100 formed with external threads and extending through anopening 56d formed in the side wall of cup-shaped member 56. Stud 100 isformed with a screw driver kerf or slot 100a and is adapted with a nut102 for adjusting the position of stationary end wall 96 for a purposeto be hereinafter explained.

Cup-shaped member 56 is formed with an opening 56a for exposing cavity560 to atmospheric conditions.

Positioned adjacent pilot burner 44 to be heated by a flame thereof, isa thermoelectric generator or thermocouple 104. An electrical conductor106 affords connection between one of the cold junctions of thermocouple104 and the enlarged end portion 78a of stationary contact member 78. Anelectrical conductor 108 affords connection between the other coldjunction of thermocouple 104 and one end of winding 37 ofelectromagnetic operator 36. The other end of winding 37 is grounded asat 110 while cup-shaped member 54 is grounded as at 112 to provide anelectrical circuit from one side of thermocouple 104 through conductor108, winding 37, grounds 110 and 112, cup-shaped member 54, mountingmember 74, bellows 90, mounting member 7 0, contacts 72 and 88 andelectrical conductor 106 to the other side of thermocouple 104.

The operation of the subject apparatus will now be described.

The first step in placing the apparatus in operation, fol lowingignition of pilot burner 44, is to energize fan 22. Operation of fan 22decreases the fluid pressure within plenum chamber 16 thereby causingthe air therewithin to be drawn through air outlet duct 20 and forced tothe chimney or stack for expulsion to the atmosphere. Such movement ofair causes air to be drawn into combustion chamber 16 through air inletduct 18, this process being continuous as long as fan 22 continues tooperate satisfactorily. The decrease in fluid pressure within plenumchamber 16 caused by satisfactory operation of fan 22, is transmittedthrough conduit 48 and causes a decrease in the fluid pressure withincavity 54c of cup-shaped member 54, whereupon the atmospheric pressurewithin chamber 560 moves diaphragm 64 so as to effect engagement ofmovable contact 72 and stationary contact 88. Engagement of contacts 72and 88 permits the electrical potential generated by heating ofthermocouple 104 by the flame at pilot burner 44, to cause electriccurrent to flow through the above-described electrical circuit includingWinding 37 of electromagnetic operator 36. Energization of operator 36,in turn, causes operating lever 38 to be pivoted against the force ofcompression spring 42 thus moving valve member 32 to its flow-permittingposition relative to valve seat 34. Thus fluid fuel is permitted to flowthrough conduit 24, control device 26 and conduit 28 to main burner 30where it is ignited by the flame at pilot burner 44 to provide a flamefor heating of the air within the plenum chamber 16 and hence the airwithin heat exchanger 23. The heated air within heat exchanger 23 isthen transmitted by any desired means such as a fan or blower (notshown) throughduct 27 to the space to be heated, such means alsobringing in cooler air through duct 25 to be heated within heatexchanger 23. It will be noted that the aforedescribed use of pressureresponsive switch 50 in circuit with thermocouple 104 and winding 37 ofelectromagnetic operator 36 requires fan 22 to be operatingsatisfactorily in circulating air from within plenum chamber 16 to thechimney or stack prior to ignition of main burner 30. Such safetyfeature insures an adequate supply of secondary air to main burner 30for complete combustion of the fluid fuel emitted therefrom.

Further, it will be seen that since bellows 98 and movable mountingmember 94 are substantially identical with bellows 90 and movablemounting member 70, any variation in fluid pressure within plenumchamber 16 caused by changes in ambient atmospheric pressure has noeffect on the differential between the control point pressure within thechamber 540 in response to which the contacts 72 and 88 engage and theambient atmospheric pressure. This is true because both of cavities 54cand 560 are exposed to atmospheric conditions and because the oppositesides of diaphragm 64 have substantially equal effective areas. It isthus seen that any variation in atmospheric pressure within cavity 54cis also realized within cavity 560 through opening 56a in member 56, sothat any increment of actuating force exerted on the diaphragm 64 andhence on the contact 72 as a result of the variation in pressure withinthe chamber 540 is opposed by an equal force resulting from the samevariation in pressure within the chamber 56c. As a result, the pressurewithin the plenum chamber 16 constituting the control point pressure ofthe device 50 bears a fixed relation to ambient atmospheric pressure,and actuation of the contact 72 into engagement with contact 88 inresponse to operation of the blower 22 is assured, irrespective ofvariations in the ambient atmospheric pressure.

I prefer to employ bellows 90 and 98 as biasing means for initiallysetting diaphragm 64 in a predetermined position wherein movable contact72 is out of engagement with stationary contact 88. Such setting can bevaried by merely changing the position of adjustable end wall 96, as byvarying the position of nut 102 on stud 100. As will be realized bythose persons skilled in the art, the initial relative position ofcontacts 72 and 88 determines the biasing force of bellows 90 and 98which must be overcome by the pressure variation within plenum chamber16 before contacts 72 and 88 are engaged. It is thus seen that theamount of pressure variation required within chamber 16 before contact72 will be caused to engage contact 88 is also adjusted by means of nut102 and stud 100. It is realized that separate biasing means may beemployed on one or both sides of diaphragm 64 in place of the biasingeffect of either or both of bellows 90 and 98 without departing from thespirit of the present invention.

Upon removal of the pressure variation within plenum chamber 16 ascaused by shut-down or faulty operation of blower 22, diaphragm 64 isreturned to its initial position under the biasing effect of one or bothof bellows and 98, thereby separating contacts 72 and 88 andinterrupting the energizing circuit for winding 37 of electromagneticoperator 36. Deenergization of winding 37 causes operating lever 38 tobe rotated under the influence of spring 42 to return valve member 32 toits flow-preventing position in engagement with valve seat 34. Thusfluid fuel flow to main burner 30 is interrupted.

Fluid fuel flow to main burner 30 will be automatically interrupted, aswell understood in the art, whenever thermocouple 104 is permitted tocool as by reason of extinguishment of the flame at pilot burner 44.

Although I have shown and described certain specific embodments of myinvention, I am fully aware that many modifications thereof arepossible. My invention, therefore, is not to be restricted exceptinsofar as is necessitated by the prior art and by the spirit of theappended claims.

I claim:

1. A control device comprising a pressure sensitive member havingopposite sides of substantially equal area and defining one wall of apressure sensing chamber, a first electrical contact fixed within saidchamber, a cooperating second electrical contact within said chamberfixed relative to said pressure sensitive member for movement therewithtoward and away from said fixed contact, hermetically sealed enclosingmeans for said contacts comprising a first variable volume containerhaving a fixed wall and having an opposing movable imperforate wall towhich said second contact is fixed, said movable wall being fixed to andreducing the effective area of said pressure sensitive member exposedwithin said chamber, and means for reducing the effective exposed areaof the opposite side of said pressure sensitive member an amount equalto the reduction effected by the movable wall of said container, saidlast-mentioned means comprising a second hermetically sealed variablevolume container having a fixed wall andhaving an opposing movable wallfixed to the opposite side of said pressure sensitive member and havingan area substantially equal to the area of the movable wall of saidfirst container.

2. A control device comprising a pressure sensitive diaphragm havingopposite sides of substantially equal area and defining one wall of apressure sensing chamber, a first electrical contact fixed within saidchamber, a cooperating second electrical contact within said chamberfixed relative to said pressure sensitive diaphragm for movementtherewith toward and away from said fixed contact, hermetically sealedenclosing means for said contacts comprising a first variable volumecontainer having a fixed wall and having an opposing movable imperforatewall to which said second contact is fixed, said movable wall beingfixed to and reducing the effective area of said pressure sensitivediaphragm exposed within said chamber, and means for reducing theeffective exposed area of the opposite side of said pressure sensitivediaphragm an amount equal to the reduction effected by the movable wallof said container, said last-mentioned means comprising a secondhermetically sealed variable volume container having a fixed wall andhaving an opposing movable wall fixed to the opposite side of saidpressure sensitive diaphragm and having an area substantially equal tothe area of the movable wall of said first container.

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